Ball, disk, and drum mechanism



Nov. 13, 1945. E. DAWSON BALL, DISK, AND DRUM MECHANISM Filed Aug. 21, 1941 INPUT SHAFT 5 1 20 E 46 n 42 67 44 Z I CO NTROLLED MEMBER |2 so so 1 Q PREDICTION CONSTANT 5| sPEEo MOTOR 6o T}ME 0F FLIGHT CAM INPUT 35 2; SHAFT 2O l 46 if E I I2 44 l 15' 5O 5 5O E o y CONTROLLED MEMBER 23 18 '11! HQ a *7 SPEED 22 INDiCATOR 50' I6 IO l4 CONTROLLED MEMBER CONSTANT SPEED MOTOR INVENTOR.

EDWARD DAWSON Z ATTORNEY Patented Nov. 13, 1945 BALL, DISK, AND DRUM MECHANISM Edward Dawson, New York, N. Y., assignor to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Application August 21, 1941, Serial No. 407,706

3 Claims.

This invention relates to ball, disk and drum mechanisms, and particularly concerns an improvement in such mechanisms applicable for use in fire control instruments as a prediction computing device or in torque amplifying instruments, tachometers or rate measuring devices or in other kindred types of apparatus.

In many forms of employment for mechanisms of this character the speed of the input shaft, i. e.

' the shaft whose speed is to be measured in the tachometer form of the device, remains at zero for extended periods of time so the normal equilibrium position of the ball carriage is such that the balls are situated at or very near the center of the rotating disc. Under such condition there is a certain amount of Sliding action between the ball in contact with the disk and the disk itself causing wear which results in a spherical depression being formed at the center of the disk. When the disk becomes worn in this manner, a much larger force is required to obtain radial movement of the ball carriage away from its central position and in addition the speed of the driven cylinder is not exactly proportional to the radial position of the ball carriage on the disk. Obviation of this condition and the attendant inaccuracy in mechanisms of this character, is the primary object of my invention.

A feature of the invention consists in the utilization in such ball, disk and drum mechanism of a first differential having an input portion thereof driven from the disk drive shaft and another input portion driven from the drum. In one of 'the forms of the invention, the output of the noted first differential is employed to drive one of the input parts of a second differential. A controlling input is provided for the other input part of the second differential and the output thereof is employed to normally position the ball carriage of the mechanism at a desired radial distance from the center of the disk. Since the contact of ball and disk then traces a circular line of appreciable diameter on the disk and since substantially pure rolling motion of the ball takes place, wear of the disk is greatly reduced and no central depression is produced.

Other objects, features and structural details of the invention will be apparent from the following description when read in connection with the accompanying drawing, wherein Fig. 1 is a diagrammatic view showing the improved ball, disk and drum mechanism as used in a prediction computing device for fire control instruments.

Fig. 2 is a similar view illustrating the mechanism applied to use in a rate measuring device, and

Fig. 3 is a further view of a similar character showing a modified form of the invention.

With reference to the drawing, the customary construction of the ball, disk and drum variable speed mechanism is shown diagrammatically in all the figures. In Figs. 1 and 2, this mechanism includes a controlling member in the form of an input shaft ID, the rotary motion of which is imparted to one part or arm of a first differential 38. The equivalent part of the device shown in Fig. 3 is constituted of a rod no whose position is controlled by a cam l0. Returning to Figs. 1 and 2, a controlled member 50' is driven by the output of the differential 38. The usual friction drive ball carriage 61, which is herein shown as including a pair of balls one rolling on the other, constitutes a portion of the controlled member through means including rack rod II,

with the rack and pinion and bevel gear connections therefor indicated respectively at 46 and I2. Driving means for the balls of the ball carriage of the controlled member are provided in each case by the disk 44 which is continuously rotated by the constant speed motor M. In the application of the mechanism to certain fire control instruments, as shown in Fig. 1, the disk 44 is capable of being driven at a variable speed which may be inversely proportional to the time of flight (T) of a shell in moving from the gun to the objective or target. To obtain this quantity, in the instant case, as shown in Fig. 1, I employ a time of flight cam 53 which is rotatably and axially positioned by means (not shown) in proportion to horizontal range and altitude of the target, the cam being so laid out that the lift of the pin is proportional to l/T. To convert this lift or displacement into a corresponding velocity of rotation, I utilize the pin 6i! to radially position a ball carriage 6| of a variable speed drive which constitutes intermediate driving means between a cylinder or drum 62 and a constantly rotating disc 63 driven by constant speed motor I4. In the embodiment of the invention shown in Figs. 2 and 3, the constant speed motor I4 is employed to directly drive the disk 44 instead of through a second variable speed gear as in Fig. 1.

The continuously rotating disk 44, in all forms of the invention drives the balls 61 of the ball carriage to thereby drive the drum member of the mechanism, as indicated at 42, when the carriage is displaced from a central position on the disk. Rotational movement of shaft 50', in Figs.

1 and 2, of the controlled member by means of input shaft Ill causes the ball carriage to move radially over the surface of the disc 44, such movement of the carriage being proportional to the change in the rotational speed of the input shaft It). In Fig. 3, the ball carriage is moved radially over the surface of disc 44 by the rod H0, the translated position of which is directed by the cam I The aforementioned parts of the described ball, disk and drum mechanism are of the usual construction and arrangement, the improvement in the same defining the present invention being provided by a differential as designated at I 4. As shown in Figs. 1 and 2, the differential I4 is employed to maintain the ball carriage of the controlled member in neutral equilibrium in an initial operating position at a desired radial distance from the center of the disk 44. In the form of the invention illustrated in Figs. 1 and 2, the differential I4 is situated between the drum and the usual output shaft provided in such a mechanism by which a return connection is made to the other input part of the first differential 38. In the illustrated forms of the improved mechanism shown in Figs. 1 and 2, one part or arm of the differential I4 is driven by the drum 42 by means of shaft [5; in Fig. 3, by means-of gear l5. To obtain the displacement of the ball carriage desired in accordance with the teachings of the invention, a further arm or portion of the differential is driven from the rotating shaft of disk 44 by means of gear connections designated at l6, l1 and I8. In Figs. 1 and 2, the sum of the inputs to the differential l4, as represented position that controlled member shaft 5!! assumes angularly is representative of the predicted movement of the target during the time of flight of a by the output thereof is returned to the other V thereby introducing a movement of the other 7 input part of the differential 38 which influences the displacement of the controlled member so I that the ball carriage is maintained in the desired initial operating position with relation to the disk 44 as will be more apparent from the following considerations.

Differential 38 serves as a speed equalizer between shafts I0 and 20. If the speeds of these two shafts are equal the speeds of the first and second arms of differential 38 connected respectively thereto are likewise equal (assuming similar gear ratios) and there is no output motion of the third arm. In the usual arrangement of the disc-ball-drum variable speed drive the ball carriage, for this condition, is positioned at the center of the disk. By introducing an additional constant component of the velocity of shaft 29, according to the invention, shaft 20 initially rotates at a faster speed than shaft in which causes an output from the third arm of differential 38. Ball carriage 61 is thereby displaced from, its central position until the displacement is sufiicient and in the proper direction to communicate to drum 42 a component velocity of rotation which neutralizes, in differential M, the velocity of the rotation transmitted by way of gears I 6 and I1 and thereby again causes shaft 20 to rotate at the same speed as shaft II].

In the embodiment of the invention shown in Fig. 1, in which the mechanism is employed to compute prediction in fire control instruments, the input shaft and gear therefrom may be driven from a present position slide as particularly shown in Fig. 4 of the patent to E. W. Chafee et al., No. 2,206,875, issued July 9, 1940., The

input parts, output means for said first differenshell. Such position may be transferred and combined with the present position indicating slide through a, further differential as shown in this patent to obtain the particular setting of. a future slide indicating the predicted position of the target. I

In the embodiment of the invention shown in Fig. 2, the positional displacement of the ball carriage at any time from its initial neutral equilibrium position on the disk is a measure of the velocity of rotation of the shaft I0 and may be visually indicated on a scale 22 by means of pivoted pointer arm 23 one end of which is suitably connected to arm ll of the controlled member.

From the foregoing description, it will be understood that for both forms of the invention shown in Figs. 1 and 2, the equilibrium position of the ball carriage, corresponding to zero input speed of the shaft I0, is not at the center of the disk, but at a fixed distance from the center which depends only on the gear ratios and drum diameter, and is independent of the speed of the disk. In the form of the invention shown in Fig. 3, the controlled member 50 is driven by the output part of differential I4, which member remains stationary when the ball carriage is situated in the desired displaced control operating position on the disk by means of cam l0. When the carriage is so positioned, the differential I4 is controlled by balanced rotational movements through pinion l5 and gear connection l1 so that the member 50' is stationary. Relative movement of the carriage from its initial operating position of neutral equilibrium through the influence of cam Ill results in proportional movement of the controlled member.

While there are above describedbut a limited number of embodiments of the invention, it is possible to produce still other mbodiments without departure from the inventive concepts above disclosed, and it is, therefore, desired that only such limitations shall be imposed on the apinput means for driving one part of said first differential, output means for said first differential, actuating means controlled by the output means of said first differential for changing the radial position of the ball carriage inproportion to the speed of operation of said input means, a second differential, input means for driving one part of said second differential from said drum, input means for driving a second part of. said second differential from said continuously rotating disk, output means for said second differential, and means for driving a second part of said first differential from the output means of said second differential to operate said actuating means and thereby normally position the ball carriage at a radial distance from the center of the disk.

2. In a ball, disk and drum mechanism, a continuously rotating disk, a radially movable ball carriage, ball means carried therein, said ball means being driven by said disc, a drum driven by said ball means, a first differential having two tial, a controlling element for driving one of the input parts of said first differential, means for moving the ball carriage connected to be operated by the output means for said first differential, a second differential, first input means for said second differential driven from said drum, and second input means for said second differential driven in accordance with the speed of rotation of said disk, output means for said second differential, and means for driving the other of the input parts of said first differential from the output means of said second difierential.

3. Means for normally positioning the ball carriage of a ball, disk and drum mechanism at' a radial distance from the center of the disk com- 15 prising a first differential having two input parts, a second differential having two input parts and an output part, means for driving one of the input parts of the first differential from the drum, means for driving the other of the input parts of the first differential from the disc, controlling means for driving one of the inputs of the second differential, output means for said first difierential, means for driving the other of the inputs of the second differential from the output means of the first differential, and ball carriage positioning means peratively connected to the output part of said second differential.

EDWARD DAWSON. 

